Method for producing bis(4-aminocyclohexyl)alkane

ABSTRACT

WHEREIN R and n are defined above, in the presence of ruthenium oxide which shows an amorphous pattern by X-ray diffraction, aqueous ammonia or liquid ammonia and an organic solvent, at a reaction temperature of 110* - 170*C, preferably 130* - 140*C under an elevated hydrogen pressure. In this method, the proportion of the resultant three kinds of stereoisomers can be varied in a wide range. WHEREIN R is hydrogen, or a methyl or ethyl group and n is 1 or 2, is made by the hydrogenation of a bis(4-nitrophenyl)alkane represented by the general formula   A bis(4-aminocyclohexyl)alkane represented by the general formula

United States Patent 91 Komoto et al.

[ METHOD FOR PRODUCING BIS (4-AMINOCYCLOHEXYL) ALKANE Inventors: 'Hiroshi Kornoto; Fusakazu Hayano, both of Saitamaken; Toshio Takami, Tokyo, all of Japan [73] Assignee: Asahi Kasei Kabushiki Kaisha,

Kitaku, Osaka, Japan [22] Filed: Oct. 9, 1970 [21] Appl. No.: 79,469

[30] Foreign Application Priority Data Oct. 16, 1969 Japan 44/82253 [52] U.S. Cl. 260/563 D, 252/472 [5 l] Int. Cl. C076 /00 [58] Field of Search 260/563 B, 563 D; 252/466 PT [56] References Cited UNITED STATES PATENTS 3,244,644 4/1966 Stiles 252/466 PT 3,193,584 7/1965 Rylander et a1 252/466 PT X FOREIGN PATENTS OR APPLICATIONS 619,706 3/1949 Great Britain 260/563 B 1,554,775 1/1969 France 260/563 D Primary Examiner-Lewis Gotts Assistant ExaminerD. R. Phillips Attorney-James E. Armstrong and Ronald S. Cornell June 26, 1973 [57] ABSTRACT A bis(4-aminocyclohexyl)alkane represented by the general formula wherein R is hydrogen, or a methyl or ethyl group and n is l or 2, is made by the hydrogenation of a bis(4- nitrophenyhalkane represented by the general formula wherein Rand n are defined above, in the presence of ruthenium oxide which shows an amorphous pattern by X-ray diffraction, aqueous ammonia or liquid ammonia and an organic solvent, at a reaction temperature of 170C, preferably C under an elevated hydrogen pressure. In this method, the proportion of the resultant three kinds of stereoisomers can be varied in a wide range.

5 Claims, 2 Drawing Figures METHOD FOR PRODUCING BIS (4-AMINOCYCLOI-IEXYL) ALKANE BACKGROUND OF THE INVENTION The production of a bis(aminocyclohexyl)alkane 5 from a bis(nitrophenyl)alkane by hydrogenation is known from the specification of French Pat. No. 1,554- ,775. In this French patent a method is disclosed in which a ruthenium compound, such as ruthenium diox ide, ruthenium-alumina, ruthenium-silica, rutheniumcarbon or the like is used. When such ruthenium compounds are used as a catalyst, the reaction must be carried out at a temperature higher than 170C, preferably higher than 200C in order to drive the reaction to substantial completion. [5

Since the reaction is exothermic, it is necessary to use low concentrations of reactant in order to achieve a reaction temperature as high as 200C. Accordingly, if it is possible to effect the reaction at a temperature lower than 170C, the reaction could be carried out safely at 0 a higher concentration. Thus the advent of a catalyst which permits the use of such a low temperature reaction is very desirable.

Accordingly, it is an object of the present invention to provide a method for aminocyclohexyl)alkane at a temperature lower than that of any of conventional methods by increasing the activity of the catalyst.

Further, it is well known that there are three kinds of stereoisomers; trans-trans, cis-trans and cis-cis for bis(- 4-aminocyclohexyl)methane. We have confirmed that the cis bond due to the presence of trans-cis and cis-cis stereoisomers exists in addition to the already known trans-trans stereoisomers.

As is well known, a high-melting polyamide can be obtained from bis(4-aminocyclohexyl)methane or bis(4-aminocycloehxyl)ethane and dodecanedioic acid. It is known that the properties of the polyamide produced from bis(4-aminocyclohexyl)methane and dodecanedioic acid varies according to the proportion SUMMARY The present invention provides a method for producing a bis(4-aminocyclohexyl)alkane represented by the general formula wherein R is hydrogen, or a methyl or ethyl group and 65 n is l or 2 which comprises hydrogenating a bis(4- nitrophenyl) alkane represented by the general formula producing a bis(4- 25 wherein R and n are defined above in the presence of a ruthenium oxide which shows an amorphous pattern by X ray diffraction, aqueous ammonia or liquid ammonia and aninert organic solvent, at a reaction temperature of l70C, preferably l30- C, under the atmosphere of pressurized hydrogen.

BRIEF DESCRIPTION OF THE DRAWING These and other objects, features and advantages of the present invention will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawing wherein:

FIG. 1 depicts an X-ray diffraction pattern of an amorphous catalyst according to the present invention; and

FIG. 2 shows an X-ray diffraction pattern of a nonamorphous catalyst according to the prior art.

DETAILED DESCRIPTION The control of the proportion of stereoisomers of diamine to a desired value in a certain range by the proper selection of reaction temperature according to the present invention has never been achieved by conventional methods and thus the industrial significance of the effect obtained by the present invention is considerable.

Among the bis (4 nitrophenyl)alkanes used in the present invention, bis(4-nitrophenyl)ethane can be produced quantitatively by bubbling air through pnitrotoluene in methanol by using NaOH at a temperature lower than 40C. In this case, a small amount of 4,4'-dinitrostilben is formed but its presence is not harmful.

The amorphous type ruthenium oxide used in the method of the invention is a precipitate obtained by neutralizing an aqueous solution of ruthenium chloride with an alkali while being careful so as not to cause a sudden change in the pH of the system or by neutralizing an aqueous solution of an alkali salt of ruthenium acid with an acid while being careful so as not to cause a sudden change of its pH. The water-containing ruthenium oxide which shows an amorphous pattern in X-ray diffraction is dehydrated by removing water from the precipitate by drying under a reduced pressure at a temperature lower than l30C. It is possible to spread amorphous type ruthenium oxide on a carrier such as active carbon, silica gel, alumina, or the like if necessary.

In the method of the present invention, 0.01 percent to about 10 percent by weight per raw material, preferably 0.2 percent to 1.0 percent by weight of catalyst is used.

In order to provide diamine in a desirable proportion of stereoisomers by the method of the present invention, a high yield can be obtained if the reaction is carried out by using the amorphous ruthenium catalyst in the presence of aqueous ammonia and an inert organic solvent under a hydrogen pressure of more than 50 kg/cm and less than 200 kg/cm at a temperature of higher than ll0C and lower than C.

The hydrogen pressure should be in the range of 50 ltg/cm to 200 kg/cm preferably 100 kg/cm to 150 ltg/cm from the view point of reaction velocity. Reaction temperatures higher than 170C, are not preferable because the proportion of stereoisomers of diamine is not suitable, and, in subsequent use, the melting point of polyamide obtained by the reaction with dodecanedioic acid is higher than 300C. Even when the reaction temperature is lower than 1 10C, the reaction proceeds but does not go completion within an economically feasible time. In the present invention, it is necessary to use aqueous ammoniaor liquid ammonia. Liquid ammonia has been used in this kind of reaction in the prior art but it has been found that any concentration of ammonia from I percent by weight to several percent by weight is useful in the present invention. It has been also found that aqueous ammonia is more effective than liquid ammonia from the standpoint of yield, etc. The amount of ammonia to be used is preferably in the range of l 100 percent by weight in the form of NH, per weight of the reaction raw materials. There is no theoretical upper limit on the amount of ammonia and 200 percent by weight or more can be used, but 5-40 percent by weight is the most practical.

The inert solvent used in the present invention must be one which is not hydrogenated under the conditions used in the reaction. In general, saturated aliphatic straight chain hydrocarbon, cyclic hydrocarbon, oxygenated saturated aliphatic straight chain hydrocarbon containing ether or hydroxy group, or oxygenated cyclic hydrocarbon containing ether or hydroxy group is suitable. In these hydrocarbons, number of carbon atoms are less than 20. Illustrative solvents are, nhexane, cyclohexane, dioxane, ethyl ether, n-butyl ether, isobutyl ether, amyl ether, tetrahydrofuran, dioxolan, dicyclohexyl ether and the like, lower, alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol and n-butyl alcohol are also useful. A mixture of more than one solvent can be used. The use of about 0.5 parts to about 2 parts by weight based on the reactant is preferable. Of course, excess solvent up to the extent of about to 20 parts by weight can be used, but such amounts only dilute the reaction mixture and this effectiveness is only for removing reaction heat.

During hydrogenation, the raw materials are hydrogenated completely to the extent of the hydrogenation of benzene nucleus. In other words, hydrogenation is carried out to substantial completion i.e. the nitro group connected directly to benzene nucleus is hydrogenated to an amino group and the benzene nucleus is hydrogenated to saturation (more than 99.99 percent).

Because the present reaction is exothermic, the removal of reaction heat at a high temperature is difficult. Accordngly, if the reaction is continued for several hours, decomposition often occurs. By the method of the present invention, it is possible to reduce decomposition effectively and to increase yields by earring out reaction at a temperature lower than that of conventional methods for 5 120 minutes. The proportion of stereoisomers to a desired value is controlled by the selection of proper reaction temperature.

The present invention has the further advantage that undesirable tarry matter or other condensation products are not produced in significant amounts.

The method of the present invention can be carried out as a batch or continuous operation.

The methods of preparing the catalyst useful in the present invention are as follows; parts and percents are by weight.

Method 1 for preparing the catalyst.

262 parts of RuCl '3l-I O,2O0 parts of water and 2 parts of IZN-HCl are dissolved in a reactor equipped with a stirrer, a thermometer and a pH meter. The mixture is neutralized with NaOH to pH 8 at room temperature while taking care so as not to cause a sudden change in pH. The resultant precipitate is filtered, washed with water and then the water is replaced by acetone. It is then dried at C for 8 hours. The X-ray diffraction pattern of the dried product is shown in FIG. 1.

Method 2 for preparing the catalyst.

523 parts of RuCl -3I-I O, 250 parts of KOH and 250 parts of KNO are melted by heating in a nickel crucible for 2 hours. After being allowed to cool by standing, the mixture is dissolved in 700 parts of water. 3,600 parts of active carbon is immersed in this solution which is then left to stand for 18 hours. Thereafter the solution is neutralized to pH 6 with 6N-I-IC1. After washing with distilled water until Cl ion is removed by using a suction filter, a catalyst is obtained by drying the washed precipitate at 1 10C for 8 hours. The X-ray diffraction pattern of resultant catalyst was almost the same with that of FIG. 1.

Our invention is further illustrated by following examples. All percentages and parts are by weight. Example 1 A solution containing of bis( 4- nitrophenyl)ethane in 75 ml dioxane and 3 g of 28 percent aqueous ammonia was hydrognated with an active carbon catalyst containing 5 percent of amorphous ruthenium oxide for a retention time of 60 minutes under a hydrogen pressure of I50 kg/cm in a high pressure vessel. The resultant product was separated from the catalyst by filtration and then solvent and water were removed by distillation. Hydrogenated completely saturated bis(4-aminocyclohexyl)ethane was obtained as a top product.

The yields of product (percent) and proportions of stereoisomers vs. hydrogenation temperature are shown in Table 1. In this table, the proportions of stereoisomers are expressed by the stereoisomers with respect to one cyclohexane ring. Namely, the proportions are expressed with the assumption that the trans-trans product corresponds to the 2 trans, the trans-cis product corresponds to the l trans and the l cis and the ciscis product correspond to the 2 cis.

to the method of Example I by using various kinds of ruthenium compounds at temperatures of C, C and 200C. The result is shown in Table 2.

It can be seen from the data that the ratio of cis to trans isomers is controlled directly by the reaction temperature used in the invention. The linear control of ratio of stereoisomers can be used to polyamide of controlled melting point.

TABLE 2 Ruthenium compounds Reaction Reaction Yield (Weight 7c/Reactant) temperature time (min.) (7:)

l. Ruthenium oxide 150C (Amorphous type) 60 96 (1 7c) 2. 170C 40 96 3. 200C 20 96 4 230C 97 5. Ruthenium dioxide (shown in H6. 2) 150C 180 2 H 6. 170C I80 5 7. 200C 120 96 8. 230C 60 95 9. Ruthenium-Alumina (involving 5 7:

of Ruthenium) 150C 180 2 7:) l0. 170C 180 3 l l. 200C 120 95 12. 230C 60 95 According to this example it is seen that amorphous type ruthenium oxides are highly active catalysts at low temperatures.

Example 3 A solution of 125 g of bis(4-nitrophenyl)methane in 75 ml of dioxane and 20 g of 28 percent aqueous ammonia are hydrogenated in a high pressure vessel, at a temperature of 150C, under a hydrogen pressure of 150 kg/cm over one part of amorphous type ruthenium oxide for a retention time of 60 minutes. The re sultant product was filtered to remove the catalyst and then diluted to remove the solvent and water. Hydrogenated and completely saturated bis(4- aminocyclohexyl)methane was obtained from the top of the column. The yield was 96 percent. The product was solid at room temperature, containing 52 percent trans material by analysis.

What is claimed is:

1. A method for producing a bis(4-aminocyclohexyl) alkane of the general formula wherein R is hydrogen, a methyl group of ethyl group and n is l or 2, which comprises hydrogenating a bis(4- nitrophenyl)-aklane represented by the general formula wherein R and n are defined above, in the presence of a catalytic amount of ruthenium oxide which shows an amorphous pattern by X-ray diffraction, aqueous or liquid ammonia and an inert organic solvent, at a reaction temperature of l l0 170C under an elevated hydrogen pressure for a time period of from about 5 to minutes.

2. A method of claim 1 wherein n=2 and R is hydrogen.

3. A method of claim 1 wherein the inert organic solvent is tetrahydrofuran.

4. A method of claim 1 wherein hydrogenation is carried out at a temperature of C.

5. A method of claim 1 wherein the pressurized hydrogen has a pressure of 50 kg/cm to 200 kg/cm gauge. 

2. A method of claim 1 wherein n 2 and R is hydrogen.
 3. A method of claim 1 wherein the inert organic solvent is tetrahydrofuran.
 4. A method of claim 1 wherein hydrogenation is carried out at a temperature of 130* - 140*C.
 5. A method of claim 1 wherein the pressurized hydrogen has a pressure of 50 kg/cm2 to 200 kg/cm2 gauge. 